code: def test_best_model2_alignment(self):
      # arrange
      sentence_pair = AlignedSent(
          TestIBMModel.__TEST_TRG_SENTENCE,
          TestIBMModel.__TEST_SRC_SENTENCE,
      )
      # None and 'bien' have zero fertility
      translation_table = {
          "i": {
              "j'": 0.9,
              "aime": 0.05,
              "bien": 0.02,
              "jambon": 0.03,
              None: 0,
          },
          "love": {
              "j'": 0.05,
              "aime": 0.9,
              "bien": 0.01,
              "jambon": 0.01,
              None: 0.03,
          },
          "ham": {
              "j'": 0,
              "aime": 0.01,
              "bien": 0,
              "jambon": 0.99,
              None: 0,
          },
      }
      alignment_table = defaultdict(
          lambda: defaultdict(
              lambda: defaultdict(lambda: defaultdict(lambda: 0.2))
          )
      )
  
      ibm_model = IBMModel([])
      ibm_model.translation_table = translation_table
      ibm_model.alignment_table = alignment_table
  
      # act
      a_info = ibm_model.best_model2_alignment(sentence_pair)
  
      # assert
      self.assertEqual(
          a_info.alignment[1:], (1, 2, 4)
      )  # 0th element unused
      self.assertEqual(a_info.cepts, [[], [1], [2], [], [3]])
  
file_path: nltk/nltk/test/unit/translate/test_ibm_model.py
imports: import unittest
  from collections import defaultdict
  from nltk.translate import AlignedSent, IBMModel
  from nltk.translate.ibm_model import AlignmentInfo
label_desc: Use image node_id 3 for calling the TestIBMModel obj's underlying member method code with example usage: obj.test_best_model2_alignment() without return types